WO1999050009A1

WO1999050009A1 - High-strength metal solidified material and acid steel and manufacturing methods thereof

Info

Publication number: WO1999050009A1
Application number: PCT/JP1999/001566
Authority: WO
Inventors: Minoru Ootaguchi; Shuji Wanikawa; Yuji Muramatsu; Kaneaki Tsuzaki; Kotobu Nagai; Toru Hayashi
Original assignee: Japan As Represented By Director General Of National Research Institute For Metals; Kawasaki Steel Corporation
Priority date: 1998-03-26
Filing date: 1999-03-26
Publication date: 1999-10-07
Also published as: EP1068915A1; US6332905B1; CN1295506A; EP1068915A4; TW520396B; KR20010074460A

Abstract

A high-strength solidified material formed by solidifying metal, such as iron, material powder by plastic working using hydrostatic pressurizing and offered as a high-strength, high-toughness steel product having an average grain size in a crystal structure of not larger than 5 νm and further an ultra-fine structure of not larger than 3 νm, one example being a steel product in which oxides not larger than 0.2 νm in diameter are dispersed at 0.5 to 60 vol.%.

Description

Description High-strength solidified metal, oxygen steel, and their manufacturing methods

The invention of this application relates to a high-strength solidified metal, oxygen steel, and a method for producing them. More specifically, a high-strength metal solidified metal powder that is easy to manufacture and has tremendous strength and elongation, and, as a type, does not require various additional elements and is lightweight The present invention relates to oxygen steel, which is a high-rigidity steel, and to a method for producing a solidified body by plastic working. Background art

Conventionally, when metal materials are manufactured by solidifying and molding powders, mechanical alloying using a ball mill is performed to increase the strength by sufficiently refining the structure, and to eliminate pores. HIP processing. Since such a conventional method for producing a solid from metal powder involves many steps, it requires not only a large number of production facilities, enormous production time and cost, but also a one-time process for batch processing. It was difficult to supply large quantities of materials to the country.

On the other hand, if solidification molding is performed without mechanical alloying or HIP processing, mass production becomes possible, but the structure of the material becomes coarse and flawed silica cannot provide sufficient strength. There were many coarse pores, and sufficient elongation and toughness could not be obtained.

Such mechanical alloying and subsequent HIP treatment is considered to be an indispensable means for the production of solidified metal powders. Therefore, it has been said that it is difficult to realize a solidified powder having higher strength and greater elongation than before.

Regardless of whether or not it is a solidified metal powder, in the case of steel, conventionally, when manufacturing high-strength materials with TS = 590 MPa or more, C, S i, M n , Nb, Cu, Ni, etc., were added by 0.22 mass% or more as appropriate in Pcm, and quenching, tempering or controlled rolling or controlled cooling was used. However, it is necessary to add various rare elements to the steel material obtained by such a method, and it is difficult to recycle the steel by using these elements. In addition, there was a problem that the heat-affected zone was hardened by welding. In addition, since the entire cross section of the steel material was difficult to have a uniform structure, there was an uneven distribution of the material inside the steel material. Disclosure of the invention

Therefore, in the invention of this application, the first technical problem to be solved is to perform mechanical alloying and subsequent HIP processing by reconsidering the above-mentioned conventional technical knowledge and common sense. It is an object of the present invention to provide a high-strength metal solidified material that can be economically mass-produced without any problem and has a strength of, for example, 450 Pa or more and a uniform elongation of 5% or more. ing.

In order to solve this problem, the invention of this application is a solidified metal raw material powder containing iron or titanium as a main component, and has an average crystal grain size of 5 ^ ΓΠ or less. Provided is a high-strength metal solidified body having a fine structure.

In addition, the invention of this application relates to the above-mentioned solidified body by plastic working by hydrostatic pressure, particularly flat rolls, groove rolls, extrudes and stamps. High-strength solidified metal solidified by at least one type of plastic working of the page, high-strength metallic solidified by plastic working using a sheath material, and Provided is a high-strength metal solidified at a temperature of 800 ° C or lower.

The invention of this application has a second problem to be solved, for example, at least 590 MPa without adding additional elements such as Si, π, Nb, Cu, and Ni. To provide a new steel material that has excellent toughness, excellent toughness, excellent weldability overcoming the problems of pre-heat treatment and heat-affected zone hardening, and has excellent recyclability. The challenge is to do that.

The invention of this application solves the above-mentioned problem, and is characterized in that it is a steel material in which an oxide having a diameter of 0.2 m or less is dispersed at a volume ratio of 0.5 to 60%. Providing oxygen steel.

Further, the invention of this application provides the oxygen steel having an average ferrite particle size of 5 m or less as a parent phase, any one of the oxygen steels having an oxygen content of 0.05 mass% or more, the tensile strength in (MP a) X uniformly elongation _(0/0) force "4 0 0 0 (P a ■%) or more, the force, one diaphragm Rica 5 is 0% or more of any of the foregoing We also provide oxygen steel.

Further, the invention of this application also provides a method for producing the above-mentioned high-strength solidified metal body and oxygen steel.

That is, in the invention of this application, a metal raw material powder containing iron or titanium as a main component is solidified by plastic working under hydrostatic pressure, and the ultrafine particles having an average crystal grain of 5 m or less are obtained. Provided is a method for manufacturing a high-strength metal solidified body, which is characterized by manufacturing a metal solidified body having a texture.

And for this manufacturing method, the plastic working is at least one of flat roll, groove roll, extrusion and swage. In addition to the manufacturing method described above, the present invention also provides a manufacturing method of performing plastic working using a sheath material and a manufacturing method of performing plastic working at a temperature of 800 ° C. or less. In addition, any one of the above-described production methods in which a metal raw material powder is milled, then plastically processed in a sealed state and solidified, and a method in which the raw material powder is a metal powder mainly composed of iron. Oxide with a diameter of 0.2 m or less is obtained by plastic working in the range of 500 ° C to the iron transformation temperature when the oxygen content of the raw material powder is 0.05 mass% or more. The present invention provides a method for producing a net material, which is dispersed at a volume ratio of 0.5 to 60%.

The raw material powder mainly composed of iron has a chemical composition of

Oxygen: 0.05-0.5 ma s s%,

Carbon: 0.1 Olmsass. /. Less than,

Chrom: 0.1 mAss ° / o or less,

Silicon: approx. 1 m s s or less,

Manganese: 0.5 mAss% or less,

The production method according to any one of the above, further comprising: BRIEF DESCRIPTION OF THE FIGURES

Figure 1 shows a stress-strain curve.

FIG. 2 is a diagram showing a metal structure observed by a transmission electron microscope (TEM).

FIG. 3 is a graph showing the relationship between the oxygen concentration, the Young's modulus, the density, and the Young's modulus density. Mode of Improvement for Carrying Out the Invention

The invention of this application has the features as described above. The embodiment will be described below.

First, at least the following two requirements are indispensable for the high-strength metal solidified body in the present invention.

<1> A solidified metal raw material powder mainly composed of iron (Fe) or titanium (Ti).

The average particle size of the crystal structure is preferably 5 m or less, and more preferably 3 m or less.

By satisfying this requirement, the present invention provides a high-strength metal solid body having a strength of 450 Pa or more and a uniform elongation of 5% or more.

For a metal raw material powder containing iron or titanium as a main component, the content of iron (Fe) or titanium (Ti) should be 50 atomic% or more in the chemical composition, more suitably 800/0 or more. Various kinds of metals, alloys, intermetallic compounds, etc. may be used. The purity does not need to be high, and a powder produced by a normal atomization method or a KIP method (a powder production method for reducing the surface scale of steel) can be used. The average particle size of the powder is preferably 100 m or less, and more preferably <30 m or less. If the average particle size of the powder is larger than 1 O Om, it is not preferable because the crystal particle size in the powder becomes coarse.

The crystal structure of the solidified product has an average particle size of 5 m or less as described above, and more suitably 3 μm or less. This is because if the size is larger than 5 jum, the effect of sufficient increase in strength due to the fine structure cannot be obtained.

What is characteristic of the high-strength metal solidified product of the present invention is that it does not require any mechanical coloring and subsequent HIP treatment, which were conventionally considered to be essential means. . High strength of the present invention without using mechanical strength rolling or HIP processing That is, a solid metal body is realized.

Means for solidification, that is, a method for producing a solidified metal body will be described. In the present invention, plastic working using hydrostatic pressure is preferably employed. More specifically, one or more of a flat mouth, a groove mouth, an extrusion, and a swage can be used for the plastic working.

It is preferable to use a flat roll, an orifice, an extrusion, or a swage for the solidification because the abnormal grain growth of the microstructure can be suppressed and a fine microstructure can be obtained by applying hydrostatic pressure. In addition, by using flat rolls, groove rolls, extrusion, or swaging, the pores inside the material are suppressed to a level that does not affect the strength and elongation. These solidification molding methods can be performed online (automated process) because they can be performed online. It is advantageous for mass production.

The solidification molding is suitably performed at a temperature of 80 ° C. or lower. At this temperature, the plastic working using the above-mentioned hydrostatic pressure is usually suitable for the area reduction of 70% or more, more preferably <80%.

The reason for setting the temperature for solidification to 800 ° C. or lower is that if the temperature is solidified at a temperature higher than this, the structure will grow abnormally and become coarse, causing a decrease in strength.

It is preferable to use a sheath material for solidification. It is considered that the sheath material is used in the shape of a tubular material, that is, a pipe, a tube, or the like. The sheath material has effects such as encapsulating and fixing the raw metal powder in a tube, facilitating the application of hydrostatic pressure during solidification and molding, and suppressing abnormal grain growth in the tissue. In order to apply hydrostatic pressure during solidification molding, it is preferable that the sheath thickness relative to the powder diameter be 1 Z 1 ◦ or more. Si There is no particular limitation on the type of stainless steel. For example, various materials such as SS 400, SΜ490, and S 45 C are applicable.

Further, the metal raw material powder may be subjected to a milling process in advance of a solidifying operation by plastic working under hydrostatic pressure. For example, treatment by planetary ball milling (at room temperature: 10 hours or more) in an inert gas atmosphere, rotating ball milling (room temperature: 50 hours or more), or the like. For example, a new steel material can be manufactured as an example of the high-strength metal solidified body described above.

For example, as described above, it is oxygen steel provided by the present invention.

In this steel material, oxide particles having a diameter of 0.2 m or less are dispersed in a volume ratio of 0.5 to 60%. The oxide particles at this time have an effect of refining the matrix structure of the steel.The smaller the oxide diameter, the greater the effect.If the diameter exceeds 0.2 ^ m, The effect of suppressing the crystal grain growth of the parent phase is reduced. If the volume fraction of the oxide in the steel structure is not 0.5% or more, the effect of refining the matrix structure is small, while if the volume ratio is 60% or more, the ductility and the ductility of the steel are reduced. And the toughness will be degraded.

For this reason, in the steel of the present invention, the size of the oxide particles to be dispersed is 0.2 m or less in diameter, and the total volume ratio of the dispersed oxide in the pot is 0.5 to 6%. 0 0/0.

Along with the dispersion of the oxide, the matrix of the steel has a ferrite structure, and it is desirable in terms of the characteristics of the steel that the average ferrite grain size be 5 or less.

In the oxygen steel of the present invention as described above, it is necessary to excessively add additional elements such as C, S i, M π, N b, C u, and N i as in the prior art. However, some of the elements that have been added conventionally do not need to be added at all. As the oxygen steel of the present invention, for example, a high-strength steel with a minimum elongation of 590 MPa and a uniform elongation of 5% or more can be obtained.

Since the dispersed oxide has a higher melting point than nitride or carbide, it remains in the weld heat-affected zone without being partially dissolved, and has the effect of preventing the matrix structure of the heat-affected zone from becoming coarse. Therefore, the heat affected zone also shows excellent toughness. In order to precipitate a sufficient amount of oxides, the amount of oxygen is about 0.05 mass. Requires / o or more.

As the volume fraction of the oxide increases, the rigidity increases and the density decreases. Therefore, by increasing the volume ratio of the oxide, a lighter-weight, high-strength steel can be provided.

In general, tensile strength and uniformity are opposite properties, and uniform tensile strength decreases as tensile strength increases.

However, the steel of the present invention has a feature that the uniformity is large together with the strength. As described above, the tensile strength (MPa) x the uniformity (%) force << 400 (P a ■%) With the above, it is considered to have extremely remarkable characteristics such as squeezing Rica <50%.

Oxide particles dispersed in the steel structure can be precipitated during production.

The conventional composition of raw materials requires only a small amount of other elements, if necessary, in addition to Fe (iron) as a basic component of steel. Almost no alloying elements need to be added. For example, regarding the constituent elements of the steel of the present invention, as mass (%), 〇 (oxygen): 0.5 or less, C (carbon) 0.01 or less, Cr (chromium): 0 0.1 or less, Si (silicon): 0.1 or less, M π (manganese): 0.5 or less, More specifically, for example, ◦: 0.2, C: 0.002, Cr: 0.05, Si: 0.02, Mn: 0.16 (mass% ) Can be used as a guide.

The powder composed mainly of iron as a raw material may be obtained by various methods, for example, by an atomizing method or a KIP method (a method of producing powder by reducing the surface scale of steel). The oxides that are deposited and dispersed can be, for example, iron oxides, Ti oxides, Cr oxides, Si oxides.

The manufacturing method of the oxide-dispersed steel of the present invention is as follows, as a typical example.

First, for example, the iron powder raw material having the above composition is milled (for example, at room temperature in an argon atmosphere) for, for example, 10 to 20 hours using a planetary ball mill or the like. Next, the milled raw material iron powder is vacuum-sealed, and then reduced at 50 ° C to 800 ° C, for example, preferably at 700 ° C (hold for 1.5 hours). Perform groove roll rolling with an area ratio of 80 <½ or more.

Of course, without being limited to the above representative examples, the manufacturing method of the present invention includes milling a metal raw material powder containing iron as a main component, and then solidifying by plastic working by isostatic pressing. It is possible to produce a steel material in which oxides with a diameter of 0.2 m or less are dispersed at a rate of 0.5 to 60% by volume, and the plastic working in this case is performed by flat rolls and grooves. At least one of roll, extrude, and swage may be used, with grooved rolls being preferred.

The oxygen content of the metal raw material powder is preferably at least 0.05 mass <%, and in order to precipitate and disperse oxides, the plasticity should be in the range of 500 ° C to the transformation temperature of iron. Processing is preferred.

Control of the oxygen content to 0.05 mass% or more is performed by various means. In order to achieve the preferred range of 0.05 to 0.5 mass%, the raw material powder can be reduced, for example, by reducing it to the required oxygen level. Are considered. In this case, the reduction treatment includes annealing in hydrogen, and the final oxygen amount can be controlled depending on the annealing time and temperature.

For the milling process prior to plastic working under hydrostatic pressure, means such as a rotary ball mill and a planetary ball mill (playable ball mill) are adopted. Generally, in the present invention, a treatment at room temperature of 50 hours or more in the case of a rotary ball mill and 10 hours or more in a case of a planetary ball mill is indicated as appropriate. . Therefore, the present invention will be described in more detail with reference to the following examples. Example

Example 1

In addition to Fe (iron) as the chemical composition, 1 iron powder containing CZO.002, Mn0.16, O / 0.2355% by weight was used under the conditions shown in Table 1. The final shape was processed into a rod-shaped test piece of 12 mm square x 800 mm.In other words, KIP iron powder was used as a sheath material and Vickers hardness 2 without ball milling and HIP. 23.Steel material (S45C) with a wall thickness of 5mm, using a tube with an outer diameter of 040x150mm and an inner diameter of 030mm, enclose the iron powder in this, At a temperature of 700 ° C, plastic working (groove roll shape: □ 40mm-□ 14.3mm) is performed by hydrostatic pressure at the groove mouth and solidified to form a rod-shaped specimen. did. A 4 × 16 mm tensile test specimen parallel to the test specimen was sampled and subjected to a tensile test. The results are also shown in Table 1. In the solidified body of the embodiment of the present invention, Showed a strength (TS) of more than 450 MPa and a uniform spread of more than 5%, though not subjected to volumizing and HIP treatment.

The average grain size of the crystal structure was as fine as 2.8 m.

Example 2

In Example 1, KIP iron powder was subjected to ball milling treatment for 30 hours in advance, and then groove roll processing was performed in the same manner as in Example 1. As shown in Table 1, the obtained solid showed a strength of 60 ° MPa and a uniform elongation of 5 <½ even though HIP was not performed. The average grain size of the crystal structure was as fine as 2.0 m.

Comparative Example 1

The KIP iron powder of Example 1 was subjected to a ball milling treatment for 200 hours and then a HIP treatment. As shown in Table 1, substantially no uniform growth was observed in the properties of the obtained test pieces.

The average grain size of the crystal structure was very large.

Comparative Example 2

The KIP iron powder of Example 1 was subjected to HIP treatment at 700 ° C. for 1 hour, and further subjected to the same groove roll processing as in Examples 1 and 2.

As shown in Table 1, the average particle size of the crystal structure of the obtained solidified product was as large as 55 μΓπ, and the strength was as small as 3966 MPa.

Comparative Example 3

In Comparative Example 2, the groove roll processing was not performed. The average grain size of the crystal structure was 23 m, and the strength was extremely small at 360 MPa. table 1

As is evident from Table 1, in the invention of this application, even if the mechanical alloying by ball milling, which was conventionally indispensable, and the subsequent HIP process are omitted, the entire material is covered. A high-strength, high-strength material having an average particle size of 5 m or less and further having a structure of 3 / m or less can be provided. For this reason, the crystal structure can be refined without the need for excessive addition of elements, which has been conventionally performed, which also contributes to resource saving and energy saving.

Example 3

After planetary milling of Klp iron powder containing C 0.02, M n /0.16, O / 0.2 mass _S % as a component other than iron for 20 h Filled into a tube of S 45 C outer diameter 40 ^ inner diameter 30 ψ, 48 〇. Vacuum canned with C for 15 hours. Thereafter, the furnace was cooled. Then 700. 1. 5 h after holding reheated and C, were subjected to grooved roll reduction by 8 ⁹ <reduction rate of ½.

Table 2 shows the results of the tensile test. It can be seen that despite having almost no alloying element added, it has greater strength than that of the comparative example and excellent uniform elongation of 7%.

Comparative Example 4

C / 0.055, Si / 0.25, MnZ1.5, Nb / O.001 1 Ni0.10, C / 0.10 mass% component steel 1 1 0 0. After holding C x 600 s, 300. CX 12 00 a was maintained and air-cooled to bainite steel. This comparative sample was subjected to a tensile test, and the results are also shown in Table 2.

Table 2

FIG. ¹ shows stress-strain curves for the steel materials of Example ³ and Comparative Example ⁴ .

The value of tensile strength (MPa) x uniform elongation (%) is 5920 (MPa '%) in Example 3 of the present invention and 2 in Comparative Example 4. It was 9 24 (MPa-%).

For those of Example 3 of Comparative Example 4, the tensile strength of ¹ 2 0 MP a high and a large uniform beauty. In other words, the steel material of Example ³ is clearly superior to Comparative Example ^{4 in} tensile strength and uniform spread.

FIG. 2 shows a TEM photograph of Example 3, and it was confirmed that the oxide was uniformly and finely dispersed in the 20 hr planetary milling material. The parent ferrite particle size is very fine, about 0.5 m. This structure existed uniformly over the entire final diameter of ^ 10.

FIG. 3 is a diagram showing the rigidity, average density and rigidity Z density of the entire steel with respect to the oxygen concentration in the steel material of the present invention. The Young's modulus increases slightly and the density decreases with increasing oxygen concentration. Less. As a result, the Young's modulus density increases. Here, the Young's modulus and the density represent specific stiffness. In other words, a higher value indicates a higher rigidity with a lighter material. High rigidity means that the material is difficult to bend. For this reason, it is possible to supply materials that are light and difficult to bend even with steel. Figure 3 shows the data of the Young's modulus of AI and Ti for comparison. This shows that the oxygen steel of the present invention is superior to AI and Ti.

It was confirmed that a steel material with excellent toughness, excellent weldability overcoming the problems of pre-heat treatment and hardening of the heat-affected zone, and high strength was provided even with little addition of alloying elements as in the past. .

Since almost no alloying elements are added, resources can be saved, costs can be reduced, and good recyclability can be achieved.

Also, in the present invention, a lighter and higher strength steel is provided. Industrial applicability

The metal solidified body of the invention of the present application is a high-strength solidified body having a strength of 450 MPa or more and a uniform elongation of 5 o / o or more without employing mechanical lining and subsequent HIP. Provided. Then, a high strength steel material having excellent toughness and weldability can be provided without adding any alloying element.

Claims

Range of request

1. A solidified high-strength metal solidified metal raw material powder mainly composed of iron or titanium, having an ultrafine structure with an average grain size of 5 m or less.

2. The solidified high-strength metal according to claim 1, which is solidified by plastic working by hydrostatic pressure.

3. The high-strength metal solid according to claim 2, wherein the plastic working is at least one of a flat roll, a groove roll, an extrusion, and a swage.

4. The high-strength metal solid according to claim 2 or 3, which is plastically processed using a sheath material.

5. The high-strength solidified metal according to claim 2, which is solidified at a temperature of 580 ° C. or lower.

6. Oxygen steel characterized by being a steel material in which oxides having a diameter of less than 2 m are dispersed at a volume ratio of 0.5 to 60% by volume.

7. The oxygen steel according to claim 6, wherein the average ferrite particle size as a matrix is 5 m or less.

8. The oxygen steel according to claim 6 or 7, wherein the amount of oxygen is 0.05 mass <s¼ or more.

9. Tensile strength (MPa) X uniform elongation (%) Force << 400 ◦ (MPa •%) or more, and drawing (%) is 50% or more. Oxygen steel.

10. Metal raw material powder mainly composed of iron or titanium is solidified by plastic working under hydrostatic pressure to form a solidified metal having an ultrafine structure with an average grain size of 5 m or less. Characterized by manufacturing A method for producing a solidified genus.

11. The manufacturing method according to claim 10, wherein the plastic working is at least one of flat mouth, groove roll, extrusion, and swaging.

1 2. The method according to claim 10 or 11, wherein plastic working is performed using a sheet material.

13. The manufacturing method according to claim 10, wherein the plastic working is performed at a temperature of 13.8 ° C. or lower.

14. The production method according to any one of claims 10 to 13, wherein the metal raw material powder is milled and then plastically worked and solidified.

15. The method according to claim 14, wherein the raw material powder is a metal powder containing iron as a main component.

16. The oxygen content of the raw material powder is not less than 0.05 mass%, and the oxide having a diameter of 0.2 ^ m or less is obtained by plastic working in the range of 500 ° C to the transformation temperature of iron. 16. The method according to claim 15, for producing a steel material in which is dispersed in a volume ratio of 0.5 to 60%.

1 7. The raw material powder mainly composed of iron has a chemical composition

Oxygen: 0.05-0.5mass. / o

Carbon: 0.01 m s s s% or less

Krom: 0.1 mAss% or less

Silicon: 0.1 m a s s or less

Manganese: 0.5 mAss% or less

17. The method according to claim 16, comprising the following components.